Treatment of distillery slop



Patented Nov. 4, 1941 TREATMENT OF DISTILLERY SLOP Ernest E. Pittman andRobert Roger Bottoms,

Louisville, I y., assignors to The Girdler Corporation, Louisville, Ky,a corporation of Delaware No Drawing. Application July 28, 1939, SerialNo. 287,053

6 Claims.

This application is a continuation in part of our copending applicationSerial No. 210,163, filed May 26, 1938, relating to improvements in thetreatment of distillery slop.

The present invention relates more particularly to an improveddistillery slop treatment involving evaporation of the waste liquid ofsuch slop. It has long been known that by the evaporation of suchliquids coupled-with the mechanical removal of suspended solids from theslop,

a large recovery of grain may be secured, and at the same time theproblem of disposal of the slop can be solved. However, there have beenmany disadvantages inherent in the heretofore employed conventionalprocesses involving evaporation, among which may be mentioned therelatively high cost of fully adequate evaporator installation andmaintenance; the necessity for providing for the absorption of therelatively large amount of evaporator sirup upon the relatively smallamount of separated grain; the relatively high cost of drying themixture of grain and sirup; and the necessity of frequent and laboriouscleaning of the evaporators.

After the larger suspended solids are removed from the distillery slopcoming from the still, the residual liquid commonly known as thin slopusually contains about 3% of total solids which percentage, however, mayvary-with the type of slop under treatment and the eiiiciency of theinitial separation step. Contained within this thin slop will be found acertain percentage of small suspended solids together with a certainpercentage of solids in solution within the slop liquid. The solids insolution may comprise certain unfermentable sugars, glycerine, solubleprotein, organic acids such as lactic and succinic, gums, resins, andthe like.

The presence of these materials interferes in a great measure with theefliciency of evaporators, and as the concentration of the same in theliquid being evaporatedincreases, they tend to foul evaporator surfacesand form a sticky heat insulating film on such surfaces. Furthermore,the high percentage of these solids inthe concentrated liquid passingthrough the later stages of evapognition of this problem and indicatesthe nature of one solution which was attempted.

In addition to mixing quantities of extraneous material with the grainin order to solve this problem, it has also been proposed to recirculatethrough the drier a suflicient quantity of grain previously mixed withsirup in order to enable it to take up the surplus amount of sirup. Suchan expedient obviously increases drier costs and entails the use ofadditional equipment.

This invention has as an object the provision of a process for reducingthe amount of solids in the thin slop passing to evaporators andproviding a greater amount of recovered solids suitable for absorbingevaporator sirup while simultaneously reducing the total quantity ofevaporator sirup produced.

Another object is to provide a process whereby evaporators may operatemore efljciently, may require less evaporator surface, may require lesscleaning and attention, and may be made of a smaller size to accomplisha given task.

Another object is to improve the efficiency of drying of solidsrecovered from distillery slop.

Another object is to provide an improved final product derived fromdistillery slop.

oration; limit ina large measure the degree to 7 which concentration canbe carried, withthe result that comparatively large quantities ofconcentrated sirup are formed in the evaporators. If this sirup is to beused in its entirety for mixing with th separated grains, it is foundthat those grain-s normally will not have sufficient absorbing surfaceto take up .all of this sirup. Reference to Geiger Patent No. 1,057,142afiords a-rec- Another object is to provide a thin slop of reduced totalsolids content by means of bentonite treatment.

Another object is to provide an improved agglomerate of distillery slopresidues and bentonite having filter aid properties enabling theagglomerate to be removed from the liquid in a rapid and efiicientmanner.

Other objects and advantages will become more apparent as the disclosureproceeds.

It is proposed to apply the invention in such a way as to adapt it bestto the particular equipment found in the particular distillery involved,and consequently the invention may be applied with respect to thetreatment of thick slop, thin slop, or mixtures of the same.

Assuming that the thick slop from a distillery is to be treated, we mixcolloidal bentonite therewith, either as a dry powder or as a slurry ofbentonite and water, or as both. By colloidal bentonite, we meanbentonite which possesses the property of dispersing in water andforming a relatively stable colloidal suspension therein.

In those cases in which the grain is given only a coarse grinding, sothat comparatively little protein goes into solution in the slop, drybentonite alone, and in the ratio of about 15 pounds of bentonite to1000 gallons of thick slop may be used, whereas in those cases in whicha finely ground grain has been employed, a slurry of bentonite in water,having a ratio of one part dry bentonite to 15 parts by weight of water,may be mixed with the slop in the ratio of about 1 gallon of slurry toabout 8 gallons of slop. It will be understood, of course, thatvariations in these ratios may be had without departing from the scopeof the invention. Ordinarily, the amount of bentonite used is seldomless than 10 nor more than 60 pounds per 1,000 gallons of slop.

The colloidal bentonite, upon being mixed with the thick slop in itsheated condition, forms an agglomerate with the larger suspended solidsand the small colloidally suspended solids, and also forms a coagulumwith certain of the soluble constituents. This agglomerate is thenseparated from the slop liquid in any suitable separatory apparatus suchas centrifugals, filters, presses, screens, gravity separationclarifiers, or the like, after which the liquid eflluent is directed toan evaporator, and the separated solids are directed toward a mixingstation.

The evaporator is preferably a multi-efiect one, and the evaporation iscontinued until the liquid becomes a thin sirup which issubstantially-free of suspended solids and dissolved protein previouslyremoved from the slop in the bentonite treatment.

The solids separated after the bentonite treatment and sirup from theevaporator are mixed in any conventional mixing apparatus, and themixture is then dried in any conventional drier. The solids from thebentonite treatment may be dried before adding th sirup, if desired, butthis requires a second drying after the addition of the sirup.

The liquid separated after the bentonite treating step has a reducedtotal solids content in contrast with the usual solids content found inthe thin slop heretofore obtained by any known commercial treatment. Theclarified liquid of our process has a negligible proportion ofcolloidally suspended material, and a reduced amount of nitrogenoussubstances, gums and resins. Of particular importance is the fact thatthe liquid is substantially free of suspended solids since experiencehas shown that suspended solids interfere with efficient evaporation toa far greater extent than do the soluble solids contained in the liquid.It appears that the presence of the substantial amount of suspendedsolids found in the liquids resulting from known treating processeslimits the degree to which concentration may be carried without cakingthe evaporator surfaces, whereas in our process the degree: to whichconcentration may be carried is limited chiefly to the point at whichthe soluble solids coming out of solution begin to cake on suchsurfaces.

The production of this relatively clear efliuent makes possibleremarkable advantages in the evaporation step of the process. The solidsin the eflluents formerly obtained exerted an inhibiting actionon theevaporation of the moisture, required large quantities of evaporatorheat, and resulted in the production of large quantities of sirupcontaining low solids content. Our process enables the distiller toobtain a very much smaller total quantity of sirup oi high solids con-'tent,.and at far less expense.

The presence of the comparatively small amount of bentonite material,plus the additional ,amountof solids removed by the use of bentoniteplus the amount of coarse solids which are always removed by the initialseparation treatment, results in the production of a larger amount ofsolid material .available for absorbing the sirup coming from theevaporators. Therefore, our process makes it possible for the operatorto mix all of the evaporator sirup with the solids derived from theseparation step, and avoids the necessity for using extraneous bulkingmaterial, although in our process some of the dried grain may berecirculated to increase the sirup absorbing surface and speed up thedrying, if desired.

In those instances wherein the invention is used in a distillery havingequipment for screening out coarse solid from the thick slop to form athin slop, the colloidal bentonite may be added to the thin slop soobtained. In such cases the agglomerate resulting from the bentonitetreatment of the thin slop may be passed through any suitable secondaryseparating apparatus as for example, a filter press. It has been foundthat the agglomerate of colloidal bentonite and solids derived fromdistillery slop possesses a remarkable filter aid property. Thefiltration of untreated distillery slop has heretofore been impossibledue to the rapid coating of filter surfaces with the colloidallysuspended particles of the slop, but in our process the agglomerateincluding the bentonite, acts as a filter surface and will not clog thefiltering surfaces of the filtering apparatus.

In carrying out the invention in this way, the

, eflluent of the thin slop coming from. the secondary filteringapparatus has a reduced total solids content as above indicated, and maybe passed directly into the evaporators. The solids separated from thisthin slop in the secondary separating apparatus preferably are mixedwith the solids separated in the initial separating or screening step.Th evaporator sirup resulting from the evaporation of the bentonitetreated thin slop may be mixed with either or both these two grades ofseparated solids, and before, after, or during the mixing and the entiremixture or the separate two grades of separated solids may be passedthrough the drying stage.

As will be apparent from the foregoing the many advantages of ourinvention result from the treatment of the slop material with colloidalbentonite. Almost every distillery prides itself upon its particulargrinding formula and its own special conditions of operation, andtherefore, it will be evident that different slops may require treatmentin accordance with their own individual characteristics. The amount ofbentonite to be used will depend to some extent upon the particular slopbeing treated, for example, that obtained from molasses or rye, corn, orother grains. We have found that in certain types of slop the additionof a small percentage of lime is advantageous in facilitating separationof solids, and in some cases permits a reduction in the amount ofbentonite required.

In certain instances wherein it is desired to effect the separation ofthe thin slop from the col.- loidal bentonite agglomerate by means ofdecantation or sedimentation, it may be desirable to add a certainamount of non-colloidal material to produce a more rapid settling of theagglomerate. In such cases, a non-colloidal material such as fullersearth or the like may be added to the treated slop to give an increasedsettling rate of the agglomerate.

Other variations of the bentonite treatment may be practiced fortreatment of slop having particular unusual characteristics, withoutdeparting from the invention.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent is:

1. The process of disposing of distillery slop including treating theslop with colloidal bentonite, said bentonite being capable ofdispersion in water and forming a relatively stable colloidal suspensiontherein, and said slop containing a sufficient quantity of colloidallysuspended solids to coagulate said suspension of colloidal bentonite, tothereby form a. separable agglomerate and a liquid having a total solidscontent of not more than 2.5% and substantially free of suspendedsolids, separating the agglomerate from the clarified liquid,evaporating moisture from the liquid to form a relatively small volumeof highly concentrated sirup, and utilizing the sirup and agglomerate.

2. The process of producing feed from distillery slop which includesscreening the thick slop to separate th coarser solids and to form athin slop, treating the thin slop with colloidal bentonite, saidbentonite being capable of dispersion in water and forming a relativelystable colloidal suspension therein, and said slop containing asufiicient quantity of colloidally suspended solids to coagulate saidsuspension of colloidal bentonite, to thereby form a separableagglomerate and a liquid substantially free of suspended solids,

evaporating the liquid to form a relatively small volume of highlyconcentrated sirup, mixing the sirup and separated solids and drying themixture to form a feed.

3. The process of producing feed from distillery slop which includestreating the slop with colloidal bentonite in the presence of lime, saidbentonite being capable of dispersion in water and forming a relativelystable colloidal suspension therein, and said slop containing asufficlent quantity of colloidally suspended solids to'coagulate saidsuspension of colloidal bentonite, to thereby form a separableagglomerate and a liquid, separating the agglomerated solids to leavethe liquid substantially free of suspended solids,.

evaporating the liquid to form a. relatively small volume of highlyconcentrated sirup, mixing the sirup and separated solids, and dryingthe mixture to form a feed.

4. The process of recovering feed from distillery slop which includestreating the slop in a. heated condition with colloidal bentonite, saidbentonite being capable of dispersion in water and forming a relativelystable colloidal suspension therein, and said slop containing asunicient quantity of colloidally suspended solids to coagulate saidsuspension of colloidal bentonite, to

thereby form a separable agglomerate and a liquid, separating theagglomerated solids to leave the liquid substantially free of suspendedsolids, evaporating the liquid to form a relatively small volume ofhighly'concentrated sirup, mixing the sirup and separated solids, anddrying the mixture to form a feed.

5. The process of producing feed from distillery slop containing asufiicient quantity of colloids to coagulate a stable suspension ofcolloidal bentonite, which includes treating the slop with bentonitecapable of dispersion in water and forming a relatively stable colloidalsuspension therein, to thereby form a separable agglomerate and arelatively large volume of liquid, separating the agglomerated solids toleave the liquid with a total solids content of not more than 2.5% andsubstantially free of suspended solids, evaporating the large volume ofliquid to form a highly concentrated sirup, the volume of which isrelatively small for mixing said sirup with the solids separated fromthe original slop without addition of extraneous bulking material, anddrying the mixture to form a feed.

6.-The process of recovering feed from distil lery slop containing asufficient quantity of colloids to coagulate a stable suspension ofcolloidal bentonite, which includes treating the thick slop withbentonite capable of dispersion in water and forming a relatively stablecolloidal suspension therein, to thereby form a separable agglomerate ofthe suspended solids and the colloidal matter adsorbed by the bentonitetogether withya reltively large volume of liquid, separating theagglomerate to leave the liquid with a total solids content of not morethan'2.5% and substantially free of suspended solids, evaporating alarge volume of such liquid to form a relatively small volume of highlyconcentrated sirup sufllciently small for mixing with the solidsseparated from the thick slop without addition of extraneous bulkingmaterial, mixing the sirup with the solids and drying the mixture toforma feed.

ERNEST E. PITTMAN. ROBERT ROGER BOTTOMS.

